The human phagocyte might be expected to be in part responsible for the limitation and eradication of chlamydial invasion. However, the relative role of this cell is not established and the various degrees of acute inflammatory response to chlamydial infections must be explained. This proposal addresses the single issue as to why the phagocyte response is limited and on what basis does chlamydia rely for its self-defense. Chlamydia, are among the few micro-organisms which survive phagocytosis, and the prevention of lysosome- phagocytic vacuole fusion is considered an important aspect of this altered host defense response, but may represent a late manifestation of deranged phagocyte activation. Our laboratory, which is devoted to the elucidation of normal neutrophil function stimulated in vitro by dormant particles and a variety of soluble agonists utilizes a multifunctional assessment of the complex cellular activation cascade. We will examine with a broad spectrum of chlamydial strains, the attachment, phagocytic rate and a battery of metabolic responses including membrane depolarization, oxidative metabolism, degranulation of primary and secondary granules, calcium flux, phospholipid turnover, arachidonic acid release and cation exchange, all of which assess various components of neutrophil activation. These parameters will be correlated with killing indices and vacuole-lysosomal fusion to establish at which point in the activation cascade chlamydia interferes with normal neutrophil response. After identifying those strains most effective in surviving phagocytosis, analysis of supernatant culture fluid and chlamydial components will be undertaken to define a putative component(s) or product(s) the organism utilizes to effect protection. Again, a comprehensive survey of neutrophil biochemical responses will be assessed with the addition of chlamydial products and constituents. The phagocyte killing mechanisms will be examined by incubating sub-cellular components with chlamydia. Preliminary studies suggest that a non-oxidative mechanism (e.g. lysosomal degradative enzymes) is responsible for the microbicidal event in this infection. Analysis of various lysosomal components and characterization of responsible enzymes will identify the microbicidal mechanism of normal host defense. These studies then are designed not only to examine the pathophysiologic basis of chlamydia infection, but serve as an important paradigm of altered phagocyte function and should enlighten us to the hierarchical cascade of normal neutrophil functional integration.